Optical device for a stereoscopic camera with a horizontal movement of the film



0a. 23, 1956 E MILLET 2,767,629

OPTICAL DEVICE FOR A STEREOSCOPIC CAMERA WITH A HORIZONTAL MOVEMENT OFTHE FILM Filed April 13, 1954 2 Sheets-Sheet 1 Q0 0 000 u no 0 0 0 0 0 uo 0 u 00 u 0 u o co H N W n 1 1 {b l 42b I 1 v UOObOOOOOOOODOOOOUtOOMllllllllllllllllllll INVENTOR Eugene Mp'lleb ATTORNEY Oct. 23, 1956 LETE. MlL 2,767,629 OPTICAL DEVICE FOR A STEREOSCOPIC CAMERA WITH AHORIZONTAL MOVEMENT OF THE FILM Filed April 13, 1954 2 SheetsSheet 2INVENTCIR Eugene Millet.

ATTOR NEY OPTICAL DEVICE FOR A STEREOSCOPIC CAMERA WITH A HOPJZONTALMOVEMENT OF THE FILM Eugene Millet, Yverdon, S. A., Sainte-(Iroix,zerland Switzerland, assignor to Paillard Switzerland, a corporation ofSwit- Stereoscopic photographic cameras with a horizontal movement ofthe film are generally equipped with two photographing objectives spacedhorizontally apart by a fixed distance in such a manner as to registereach of the images taken at a different angle. This distance, called thebase, is approximately equal to the spacing of the eyes. The objectivesare secured to the camera in such a manner that their optical axesconverge at a given distance, permitting an admissible superposition oftwo images of the stereoscopic couple. When this arrangement is rigid,it does not permit filming any object whatsoever, because, duringprojection, a convenient stereoscopic perception is only possible whenthe two extreme frontal planes of the object are located between twowell defined limits. The zone comprised between these two limitsconstitutes the depth of stereoscopic field. It is defined by thedeviation in convergence which perception of the relief can toleratewithout fatigue. For this reason, it is necessary to be able to displacethe point of convergence of the two optical axes of the camera, in sucha manner as to permit filming subjects located at infinity to a distanceconsidered as a minimum for taking views.

On the other hand, when taking stereoscopic views on a film movinghorizontally, two images of the same pair of images are generally spacedin a vertical direction, this vertical spacing depending on the width ofthe film. Whilst for small sizes, this spacing can be tolerated, on thecontrary for a larger size, such as 35 mm. for example, it becomesdeleterious and must be annulled.

Some devices are already known which permit the displacing, in avertical direction, the two luminous beams passing through the openingsfor taking views of a stereoscopic camera. These devices utilise, ingeneral, two groups of two prisms with apices opposed relatively to oneanother, located on each of the beams passing through a photographingwindow. There are known, on the other hand, especially in sometelemeters, combinations of prisms turning relatively to one another andpermitting the producing of a continuous deviation of a luminous beamprecisely by rotation of one prism relatively to the other.

The device according to the invention is of the type comprising twoidentical optical groups, adapted to be each located in front of aphotographing window, each optical group comprising an objective and anassembly of prisms. This optical device is distinguished from knownoptical devices of this type by the fact that the said assemblycomprises three prisms, a stationary prism being located in front ofeach objective, for deviating in a vertical plane and in the oppositedirection, the beam of each objective. prisms capable of being set inrotation in the opposite direction about an axis parallel to the axis ofthe corresponding objective, said two prisms being located on the beamof each of the said objectives for deviating, in a horizontal plane, thetwo beams, in such a manner as to Each assembly also comprises two nitedStates Patent Office 2,767,629 Patented Oct. 23, 1956 cause them toconverge on a continuous series of points. The ratio of driving of thesaid two prisms and the deviaticn which said two prisms subject thebeams which pass through them are so selected that the deviation in thevertical plane of the beam passing through the two prisms is alwaysequal and of opposite direction to the deviation in a vertical plane ofthe first stationary prism so that the total vertical deviation isalways zero, the vertical spacing between the emerging beam and theincident beam of each optical group being thus maintained constantirrespective of the distance of convergence of the two beams.

One form of construction of a device according to the invention is showndiagrammatically in the accompanying drawings, wherein:

Fig. 1 shows a fragment of a film comprising two rows of images printedin a camera, in which the film moves horizontally.

Fig. 2 shows a diagram of the principle of the device according to theinvention.

Fig. 3 shows, in perspective, the general arrangement of the objectivesand of the prisms in a camera for taking stereoscopic views withhorizontal movement of the film.

The film 6, of which a portion is shown in Fig. 1, comprises a soundtrack 7 and two rows of images printed according to a known process byhorizontal movement of the film. The images 11a and 11]) have beenprinted simultaneously and represent the same scene taken at a differentangle. The distance a which separates the images 11a and 11b should besufiicient for giving an impression in relief. It is, in general,approximately equal to the spacing of the eyes. Further, the two imagesof the same pair are each located on a half of the film so that thereremains between them a vertical spacing b. The images 12a and 121) havebeen printed in the same manner as the images 11a and 11]), but at adiiferent moment. The same applies to the images 13a and 13b and so on.

In Fig. 2 is shown diagrammatically one of the two identical opticalgroups, adapted to be mounted on the camera to permit of the registeringof the pairs of stereoscopic images, such as those shown in Fig. 1. Eachof these groups constitutes an optical passage comprising an objective 5and three prisms 1, 2 and 3. The prism 1 is stationary relatively to thecamera, whereas the prisms 2 and 3 are movable angularly relatively toone another, that is to say that they can be set in rotation in theopposite direction to one another, about an axis parallel to the axis ofthe corresponding objective 5. Said two prisms 2 and 3 are selected insuch a manner as to permit, according to the known principle, thehorizontal deviation (perpendicularly to the plane of the drawing inFig. 1) of the principal ray 4.

In Fig. 2, the prisms 1, 2 and 3 are shown by considering the plane oftheir principal section as being located vertically, that is to say inthe plane of the sheet of the drawing. The angles a1, a2 and :13represent the angles subtended by the two faces of each of therespective prisms 1, 2 and 3. The deviation produced on the principalray 4 in the plane of the principal section of the prisms is indicatedrespectively by 61, 62, 53. The distance separating the prism 1 from theprism 2 is indicated by ah, the distance separating the prisms 2 and 3by d2. Further, in Fig. 3, which is a view in perspective of the twooptical groups, the angles formed between the plane of the main sectionof the prisms 1, 2 and 3 with the horizontal plane are shown by theletters (pl, 52, 3.

As it is necessary for the total deviation in a vertical plane, producedby the prisms 2 and 3 to be constant, equal and in the oppositedirection to the deviation 61 produced by the prism 1 on the principalray 4, it is necessary to select the deviations 61, 62, 63 and theangles 51, p2, 53, according to a determined relation. This relation isas follows:

[i front of, and adjacent to, the objective, and two prisms each mountedfor angular rotation with respect to each other about the axis parallelto the axis of the objective, said two prisms being positioned in thebeam passing 5 through the objective, and rotating means for deviatingThe horizontal deviation 5,, necessary for the conververfic'ffl Plang ibeam. pas.sing thrmigh g W of two beams should satisfy the followingcondi- Pmmsequany m the dmictlon opposlte to e gene? tron of the beam inthe vertical plane of the stationary prism means, said rotating meansbeing operatively con- 6 =6 cos +6 cos +6 9 P 1O nected to said prisms,whereby the total vertical deviation of the beanis always zero therebymaintaining constant In the parti ular case, Where all the Prisms 1, 2and 3 the vertical spacing between the emerging beam and the areconstructed of glass of the same quality, it is possible imidgnt beam feach i group d h b h to y that the condition to be satisfied is that thebeams deviate in the horizontal plane in a variable manference in theangles between the sections of the two faces Her thereby causing Saidbeams to Converge at a d f a of the tWO y Prisms Z and 3 in a Vamcaltermined series of points at a predetermined distance plane, passingthrough the axis of the corresponding f the camera objective, is equalto the angle between the two faces of 2 A stemoscopic camera h i h fihmoves i. the stationary prism 1- zontally, comprising, in combination, afront plate hav- In example described above: it is assumed that the ingtwo spaced exposure apertures and two optical sys- Opiical axes 0f twoObjectives 5 Of 1116 camera tenis mounted in front of said front plate,each optical Vefgfi, hxample at 2 The hOfiZOhtal deviation system beingpositioned in front of each exposure aperthe W0 Principal rays 4 isProvided in a 1113111161 ture and comprising an objective adjacent theaperture as to permit of the movement of the point of convergence d angssgmbiy of prisms gmprising 1 11 a n a Continuous Series of Points onpp Sides of the tionary prism means for deviating beams in verticalplanes distance of 2 m. This continuous series may be extended, iOppgsife di i id Prism means being 1- for eXample from infinity t0 Y Wayof example tioned in front of, and adjacent to, the objective, and two anumerical example is shown hereinafter indicating the prisms h t d fangular t i i h respect Values relating to an Optical device adapted toq p a to each other about the axis parallel to the axis of the Vstereoscopic Camera for 35 films- T r i objective, said two prisms beingpositioned in the beam viation 51, which III13lI1S 'CC'l'lStaHt, permitsOf maintainpassing h gugh the Objective, said stationary prism ing fo hpassage a on tant vertical spacing c of means and said two prisms beingof similar glass, the 5.5 mmbfitwefin U16 emerging beam and the incidentangle between the two faces of said stationary prism am, h VerticalSpacing 5 f0 be eliminated being means being equal to the difference inthe angles between 11 m. The horizontal deviation 6 in this example maythe sections of the two faces of each of the said prisms vary in such amann r a t permit of filming ct respectively, said two prisms being in avertical plane located at a distan e D fr m th C fa P g from through thehorizontal axis of the corresponding obinfinity up to 0.50 m. jective,and rotating means for deviating in a vertical By Aria, A 3 respectivelyare indicated the variations plane the beam passing through said twoprisms equally of the angles 2 and an during the angular movements 40and in the direction opposite to the deviation of the beam of the prisms2 and 3. in the vertical plane of the stationary prism means, saidNumerical table p3 l Am I gag Am 51 5 D 4730 730 93 1'30" 34'30" 54350"31'50" 4.18 m. -90 0 90 0 543'50" 0 2 8230' 730 865530" 34'30" 543'50"s1'50" 1. 31 75 15 8351 69 54350" 13'40" 0. 93 6730 2230 8046'30"-913'30" 543'50" 134'50" 0.78 60 30 42 12l8 543'50" 25'20" 0. 66 -5230'3730 7437'30" 1522's0" 543'50 235'20" 0. 57 45 7133 1s27' 543'50" 3340"0.

As shown clearly in the above table, the optical device rotating meansbeing operatively connected to said two described, although onlycomprising two assemblies of prisms, whereby the total verticaldeviation of the beam three prisms, permits effectively, a continuousvariation is always zero thereby maintaining constant the vertical ofthe point of convergence of the two optical saXes pass spacing betweenthe emerging beam and the incident beam ing through the photographingwindows, whilst permitof each optical group and whereby the beamsdeviate in ting the eliminating of the vertical spacing of the latter.60 the horizontal plane in a variable manner thereby caus- It will beunderstood that each of the prisms 1, 2 or 3 ing said beams to convergeat a predetermined series of may be formed by a prism composed of anumber of points at a predetermined distance from the camera. elementaryprisms of glass of diiierent quality.

I Claiml References Cited in the tile of this patent 1. A stereoscopiccamera wherein the film moves hor1- UNITED STATES PATENTS zontally,comprising, in combination, a front plate having two spaced exposureapertures and two optical systems 1,299,498 Richal'd 1916 mounted infront of said front plate, each optical system 11815303 MOTaZ July 21,1931 being positioned in front of each exposure aperture and 2,453,075Land 1948 comprising an objective adjacent the aperture and an assemblyof prisms comprising essentially a stationary FOREIGN PATENTS prismmeans for deviating beams in vertical planes in 319,723 Great BritainJan. 2, 1929 opposite directions, said prism means being positioned inFrance May 4, 1936

